SOMEWHERE on the Eastern Seaboard, in a house whose residents prefer to remain anonymous, is perhaps the most revolutionary “bathroom” in America. It is not really a bathroom, but rather an indoor wetlands, constructed in specially designed tanks in a greenhouse, in which aerobic microbes, snails, fish, hibiscus and splendiferous wetland plants of nearly every description have been recruited to do the deed that a septic tank used to do.

This surreptitious biological sewage system is not legal inside single-family homes yet (and it’s doubtful snails will ever replace Sani-Flush). But in these ecologically trying times, perhaps no design problem is as poignant as the quest for the perfect toilet.

Around the country, homeowners and communities fed up with overdevelopment, contaminated ground water and overflowing septic tanks are turning to novel solutions to dispose of waste ecologically. Although their numbers remain small, they are growing, as more stringent laws proliferate, like Title 5 in Massachusetts, which requires homeowners with on-site septic systems to meet new environmental and public health standards before building an addition or selling a house.

Those in search of the trenches of eco-design need look no further than the constructed wetlands that are popping up in hundreds of backyards across the country, among people who wouldn’t previously have considered themselves “green.” In place of conventional drain or leach fields, wetland plants like cattails, reeds and bamboo are sprouting. Unlike a conventional septic system, the water is not destined simply to go into the ground, but rather to be absorbed by the roots of plants.

Others are turning to composting toilets, which use peat moss and sawdust in place of water. In Taos, N.M., one group has even begun marketing a build-it-yourself solar toilet. They have borrowed the motto of the Starship Enterprise: “To boldly go where no man has gone before.”

“We have to get beyond flush-and-forget technology,” said Sim Van der Ryn, founder of the nonprofit Ecological Design Institute in Sausalito, Calif., and author of “The Toilet Papers: Recycling Waste and Conserving Water.”

“The main bent is to deal with one’s own waste as close to the source as possible,” Mr. Van der Ryn said.

At Sam and Wendy Hitt’s house in Santa Fe, N.M., on a patch of semiarid land once farmed by the Anasazi Indians, the sight of cattails and bulrushes amid the wild sage and chamisa “does stand out,” Ms. Hitt said. She and her husband, the director of Forest Guardians, a forest conservation organization, moved into a house with what she called a terrible septic system and drain field. “We wanted to try something different that had less impact on the land,” she said.

Waste water is piped from the Hitts’ conventional septic tank to a specially designed lined bed layered with water, gravel and vegetation. As it moves slowly through this wetland, chemical reactions and microbial activity in the plants absorb and assimilate harmful substances, including nitrogen and phosphorous compounds that can cause rampant algae growth and might otherwise be pollutants. Solids remain in the septic tank. The system is designed so that the waste water remains underground during the weeklong process, without providing malodorous competition to the intoxicating scent of Santa Fe pinon. Once the water is purified (recyclable but not drinkable), it meanders on to the Hitts’ drip-water irrigation system that nourishes the squaw bush and ponderosa pines they have planted as a windbreak.

In places like Taos County, where uncontrolled growth has resulted in ground water pollution from septic tanks, the backyard wetland trend is in its infancy, but “growing rapidly,” said Alfred Krause, a water expert with the Environmental Protection Agency in Chicago. Current estimates range from 800 to 3,000 individual systems nationwide, most in Kentucky, Mississippi and Louisiana, states that have detailed guidelines. Between 400 and 500 communities have built wetlands on a broader scale as a more natural alternative to conventional sewage treatment plants, he said.

At the Arcata Marsh and Wildlife Sanctuary in Northern California, residents in 1986 inaugurated their new sewage system, which is ringed with bird watchers with spotting scopes on busy days, by holding a Flush With Pride festival.

One problem with individual, backyard wetlands is cost, at least initially. Morton Nilssen, a residential specialist with the Southwest Wetlands Group in Santa Fe, said a backyard wetland is about two and a half times as expensive to set up as a traditional septic system. Wetlands also need nurturing, preferably by a specialist trained to guide a natural system.

The advantages may be greater for a small community. In a study of 30 ecological treatment plants, construction costs were from 10 to 50 percent lower than for a conventional sewage treatment plant, Mr. Krause said. They are also easier to operate and do not require tons of concrete and large amounts of chemicals.

In Indiana, the state’s Department of Health has classified backyard wetlands as experimental systems that must be monitored by county health departments. The LaGrange County Department of Public Health began a constructed-wetland program for single-family homes last month, spurred by a public health crisis from contaminated ground water that has caused upper respiratory and gastrointestinal disorders in the county. Septic tank technology invented in 1874 has been stretched beyond the limit as the population expands, said Bill Grant, the county administrator.

His department now provides homeowners with blueprints. A wetland for a typical three-bedroom house would be about 14 feet by 25 or 30 feet, about the size of the floor space in a two-car garage.

“Constructed wetlands are probably not the last word, but we’ve got to start someplace,” Mr. Grant said.

An impediment to this and other unconventional approaches has been what he calls a “by-the-book mentality,” a Catch-22 patchwork of regulations, which vary from county to county.

But the problem remains this, Mr. Krause said: “Every day, under the best of circumstances, we use 1.6 gallons of drinking water to flush half a pint of waste.”

Ultimately, Mr. Krause said, economics, including the phasing out of Federal construction grants for local waste-water treatment, may force Americans to consider the alternatives. These include composting toilets, which allow bacteria and fungi to break down waste to humus, and are harvested about once a year. Composting toilet enthusiasts number only in the thousands.

The grandmother of composting toilets is the Clivus Multrum (a Latin-Swedish amalgam that means “inclining compost room”), developed in Sweden in the 1930’s. The Clivus is distributed in the United States by a company run by Abby Rockefeller, David Rockefeller’s daughter.

Many of the compact toilets look like glorified potties. There are other psychological hurdles, even among former hippies like J. Baldwin, a senior editor of The Whole Earth Review in Sausalito, who has lived in a converted chicken coop. “If you can’t get your teen-ager to clean up his or her own room, what is going to happen with the composting toilet?” he asked.

John Douglas and Joan Waltermire, a graphic designer and museum curator in Vershire, Vt., who have had a Norwegian composting toilet for 10 years, remember the first time they emptied it, with a shovel and much trepidation. “It smelled like forest soil!” he said. “The only problem was, the instructions were in Norwegian.”

Mr. Krause of the E.P.A. said, “Some composting toilets work marvelously, some abominably.” In an ideal world, he said, composting collectors would be as ubiquitous as garbage collectors. But he wondered, “Is America ready for the Good Humus man?”

At the least, homeowners can consider replacing old plumbing fixtures with low-flow toilets and shower heads, as was done citywide in San Simeon, Calif., where water use was cut by 50 percent, he said.

A poetic alternative is the “living machine” concept pioneered by John Todd, a Massachusetts biologist and an advocate of living more lightly on the land.

At Corkscrew Swamp, a National Audubon Society sanctuary near Naples, Fla., visitors can experience a living machine. To get to the bathroom, they walk through an aluminum screened enclosure into what seems to be a garden, a space with plastic tanks and lined trenches brimming with native marsh plants and species. These natural decomposers — what Jan Beyea, an Audubon senior scientist, calls “nature’s wonderful garbage men” — purify the waste water, 90 percent of which is then recycled for yet another flush.

The E.P.A., which has financed four living-machine demonstration projects across the country, awaits results of an independent study to determine whether their performance is “sustainable over the years,” said Robert Bastian, a senior environmental scientist with the E.P.A.

But the living machine already has its passionate adherents, including the cartoonist Jim Davis of “Garfield the Cat” fame, who has installed a Solar Aquatic system, a type of living machine, in a large greenhouse in Indiana on the property of his studio, Paws Inc. It is operated by a full-time horticulturist, Russ Vernon, who describes his job as “taking care of Garfield’s litter box.”

Because the technology is still considered experimental, Mr. Davis ran the risk of being shut down by the state if clean water requirements were not met. But so far, he said, “it’s performed like a champion.”

He added: “The only thing that’s stopping the growth of this kind of operation is tradi tional thinking.”